This invention relates to a magnetic sensor for detecting rotation or the like.
Japanese Laid-Open (Kokai) Utility Model Application No. 111662/87 discloses a rotation detecting device having a magnetic sensor. This conventional rotation detecting device will now be briefly described with reference to FIG. 5. The rotation detecting device comprises a magnetic sensor 10', and a sensing plate 20' (member to be sensed) fixedly mounted on a rotatable shaft 25' for rotation therewith. The magnetic sensor 10' and the sensing plate 20' cooperate with each other to sense or detect the rotation of the rotatable shaft 25'.
In the above rotation detecting device, the outer peripheral surface of the sensing plate 20' is so magnetized as to have alternate north and south poles. The magnetic sensor 10' includes a cylindrical sensor housing 11' which is supported on a support member 30' disposed adjacent to the sensing plate 20'. The sensor housing 11' extends toward the sensing plate 20', and has a front end disposed in opposed relation to the outer peripheral surface of the sensing plate 20' A Hall element (magneto-electric transducer) 14' is fixedly secured to the front end of the sensor housing 11'.
In the magnetic sensor 10' of this type, a clearance d' (hereinafter referred to as "magnetic gap") between the outer peripheral surface of the sensing plate 20' and the front face of the Hall element 14' influences the sensing performance or ability of the magnetic sensor 10'. It has been difficult to adjust the magnetic gap d' highly precisely when mounting the magnetic sensor 10' on the support member 30'.
Japanese Laid-Open Utility Model Application No. 182414/87 and Japanese Laid-Open Patent Application No. 82918/85 also disclose magnetic sensors similar in construction to the above magnetic sensor 10'.